Re: Goal for conversion tracking across subdomains

If your tracking is, as you say, cohesive across the subdomains up to the top level domain (TLD) and the TLD is the same, and you are using Universal, there is really nothing extraordinary you need to do.

Simple create the goal based upon the thank you page and you can use the reverse goal path report to see the previous three pages. You could also set a session level custom dimension to flag the origin subdomain if there are many and use that for reporting.

Lastly if the URI of the pages across subdomains and the TLD are the same (/ or /aboutus, etc.) then you could use an advanced filter to prepend the hostname to the uri so that the hostname is exposed in the content reports e.g. play.domain.com/signup domain.com/signup. This could also make it easier for you to set up goal funnels.